It is proposed to synthesize and study the kinetics and mechanisms of reactions of oxygen transport hemoprotein model compounds. Model compounds, which have been shown to bind O2 and CO with the kinetics and equilibria of R-state hemoglobin, will be structurally varied and their kinetics and equilibria of reaction with oxygen and carbon monoxide studied. This will allow the evaluation of proposed effects of proximal basicity, proximal strain, proximal base hydrogen bonding, base dissociation, distal side steric effects, and site polarity on oxygen affinity. Additional T-state model compounds will be prepared and studied. Diheme compounds will be prepared and studied in an effort to model cooperativity in hemoglobin. The kinetics of reaction of hemoproteins and model compounds with CO at low pH will be compared in order to establish the possible occurrence of the base-elimination mechanism in hemoprotein reactions.